<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <link rel="stylesheet" href="./01.css" />
    <style>
      html {
        /* 定义CSS变量 */
        --main-color: #C00000;
      }

      .box1, .box2 {
        /* background-color: #C00000; */
        background-color: var(--main-color);
      }

      .box3 {
        /* color: #C00000; */
        color: var(--main-color);
      }
    </style>
  <body>
    <div class="container1">
      <div class="box1">box1</div>
      <div class="box2">box2</div>
      <div class="box3">box3</div>
    </div>

    <div class="container2">
      <div class="box1">box1</div>
      <div class="box2">box2</div>
      <div class="box3">box3</div>
    </div>
  </body>
</html>
